When hitting F10, it will return the code twice, unlike all other keys, where it returns the code once, waits a moment before returning the second keystroke.
The following code reproduces it on Reaper 5.941 and Reaper 5.96 sucessfully.

I'm using Windows 7Pro, with a naked Reaper 5.96 and SWS installed.

Code:

gfx.init()
function main()
A=gfx.getchar()
if A>=1 then reaper.ShowConsoleMsg(A.."\n") end
if A~=-1 then reaper.defer(main) end
end
main()

There's also an issue with the Euro-currency symbol €
This returns two codes, 261 and 128. Is this intentional? Are there other characters that can be returned that way?